Bis(2-fluoro-2,2-dinitroethoxy)acetonitrile and a method of preparation

ABSTRACT

Bis(2-fluoro-2,2-dinitroethoxy)acetonitrile, N.tbd.C--CH[OCH 2   CF(NO..2) 2  ] 2 , is useful as a coplasticizer with bis(2-fluoro-2,2-dinitroethyl)formal in energetic plasticizer mixtures for plastic bonded explosives.

BACKGROUND OF THE INVENTION

This invention relates to plastic-bonded explosives and moreparticularly to energetic plasticizers for plastic-bonded explosives.

Examples of energetic plasticizers which are currently used inplastic-bonded explosives (PBXs) arebis(2-fluoro-2,2-dinitroethyl)formal (FEFO), butanetriol trinitrate(BTTN), and trimethylolethane trinitrate (TMETN). These compounds havevarious disadvantages which include limited thermal stability (BTTN,TMETN), high volatility (FEFO), toxicity (FEFO), and high melting point(FEFO).

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide a novel organiccompound.

Another object of this invention is to provide a new energeticcoplasticizer for plastic-bonded explosives.

A further object of this invention is to provide an energeticcoplasticizer having good thermal stability.

Still another object of this invention is to provide new energeticplasticizer mixtures.

A still further object of this invention is to provide an energeticplasticizer mixture having the same high energy content as FEFO but alower volatility than FEFO.

These and other objects of this invention are achieved by providing anew compound bis(2-fluoro-2,2-dinitroethoxy)acetonitrile and a method ofpreparing it.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention provides bis(2-fluoro-2,2-dinitroethoxy)acetonitrile(CYANO-FEFO), N.tbd.C-CH[OCH₂ CF(NO₂)₂ ]₂, a new composition of matter,which has been found to act as a coplasticizer forbis(2-fluoro-2,2-dinitroethyl)formal (FEFO) in combination with variousenergetic and non-energetic prepolymers commonly used in plastic-bondedexplosive (PBX) formulations.Bis(2-fluoro-2,2-dinitroethoxy)acetonitrile is a low melting solid (MP41°-2° C.) with a liquid density at 23° C. of 1.62 g/cm³. Its heat offormation is estimated to be -175 Kcal/mol, and the calculateddetonation pressure is 244 Kbar.

The use of bis(2-fluoro-2,2-dinitroethoxy)acetonitrile (CYANO-FEFO) as acoplasticizer for bis(2-fluoro-2,2-dinitroethyl)formal (FEFO) providesseveral advantages over the use of FEFO as a unitary plasticizer.CYANO-FEFO is equal to FEFO in energy content (detonation pressure).Therefore, its addition to FEFO does not change the energy content ofthe system. CYANO-FEFO is miscible with FEFO in all proportions, andforms a binary eutectic of the approximate composition,FEFO:CYANO-FEFO=65:35, MP 5° C. Thus, the addition of this amount ofCYANO-FEFO results in a significant decrease of the plasticizer meltingpoint; this will convey improved lowtemperature properties toplastic-bonded explosives (PBXs) using the plasticizer mixture in placeof neat FEFO. The volatility of CYANO-FEFO was determined bythermogravimetric analysis (TGA) at 117° C. The weight loss was 0.003mg/min, compared to 0.039 mg/min for FEFO. Thus, the volatility ofCYANO-FEFO is lower than that of FEFO by a factor of ten. The volatilityof the plasticizer mixture will therefore be substantially lower thanthat of neat FEFO, and the volatility of FEFO will be reduced because ofits reduced concentration.

The weight ratio of bis(2-fluoro-2,2-dinitroethyl)formal (FEFO) tobis(2-fluoro-2,2-dinitroethoxy)acetonitrile (CYANO-FEFO) in theenergetic plasticizer mixture is preferably from 1:1 to 4:1, morepreferably from 3:2 to 4:1 and most preferably about 13:7. Note thatother energetic plasticizers may also be used in the plasticizermixture. For example bis(2-fluoro-2,2-dinitroethyl)amine (BFDNA) workswell with CYANO-FEFO as a coplasticizer.

Bis(2-fluoro-2,2-dinitroethoxy)acetonitrile can be prepared from2-fluoro-2,2-dinitroethanol by the following reaction sequence asdescribed in examples 1, 2, and 3: ##STR1##

Tris(2-fluoro-2,2-dinitroethoxy)methane, CH[OCH₂ CF(NO₂)₂ ]₃, is a priorart compound which is synthesized by reacting three moles of2-fluoro-2,2-dinitroethanol with one mole of chloroform by refluxing thereactants in the presence of ferric chloride as a catalyst. Theconditions of this reaction are illustrated by example 1 which isincorporated from U.S. Pat. No. 3,388,147, entitled"2-Fluoro-2,2-Dinitroethyl Carbonates and Production thereof," which wasissued on June 11, 1968, to Mortimer J. Kamlet et al. (see col. 3,example III).

Next, the tris(2-fluoro-2,2-dinitroethoxy)methane is refluxed withaluminum chloride and acetyl chloride to produce chlorobis(2-fluoro-2,2-dinitroethoxy)methane as illustrated by example 2.

Finally, one mole of cyanotrimethylsilane is reacted with each mole ofchloro bis(2-fluoro-2,2-dinitroethoxy)methane to produce the desiredproduct, bis(2-fluoro-2,2-dinitroethoxy)acetonitrile, under conditionsillustrated by example 3. The choice of a solvent for this step is notcritical. Any inert solvent in which the reactants are soluble and whichhas a suitable boiling point may be used. Suitable solvents includedichloromethane, 1,1-dichloroethane, 1,2-dichloroethane,1,1,2-trichloroethane, or mixtures thereof.

The general nature of the invention having been set forth, the followingexamples are presented as specific examples thereof. It will beunderstood that the invention is not limited to these specific examplesbut is susceptible to various modifications that will be recognized byone of ordinary skill in the art.

EXAMPLE 1 (Prior Art)

Tris(2-fluoro-2,2-dinitroethoxy)methane [i.e.,tris(2-fluoro-2,2-dinitroethyl)orthoformate]

"A mixture of 0.5 g. anhydrous ferric chloride and 10 ml. chloroform wasplaced in a 30 ml. round-bottom flask fitted with a magnetic stirrer anda reflux condenser connected through a bubbler to a methanol gas trap.2-fluoro-2,2-dinitroethanol, 2.0 g. (0.013 mole) was added and themixture stirred and refluxed for 24 hours, after which time the mixturewas collected [sic] to room temperature and the solvent removed invacuo.

The residue was drowned in iced water, stirred until the ferric chloridedissolved and the crystalline product collected. Recrystallization ofthis material from chloroform-hexane gave 1.39 g. (68%) puretris(2-fluoro-2,2-dinitroethyl)orthoformate (FDNEOF) as fine colorlessneedles, M.P. 110°-111.2°."

EXAMPLE 2

Chloro bis(2-fluoro-2,2-dinitroethoxy)methane

A solution of tris(2-fluoro-2,2-dinitroethoxy)methane (23.6 g, 0.050mol), aluminum chloride (12.0 g, 0.090 mol) and acetyl chloride (200 g)was refluxed for 1.5 hours and then concentrated on a rotary evaporatorto a viscous liquid. This was extracted with chloroform (2×50 ml). Aftertreatment with activated charcoal (2 g), this solution was filtered andconcentrated (rot. evap., 40° C. bath) to 23 g of residue from which8.53 g (87%) of 2-fluoro-2,2-dinitroethyl acetate (bp 40°-3° C./0.1 mm)was removed by distillation. The residual liquid (14.14 g, 80% yield)was chloro bis(2-fluoro-2,2-dinitroethoxy)methane, free of contaminantsby ¹ H NMR analysis.

Anal. Calcd for C₅ H₅ ClF₂ N₄ O₁₀ : C, 16.94; H, 1.42; Cl, 10.00; F,10.72; N, 15.80. Found: C, 17.10; H, 1.78; Cl, 10.08; F, 10.71; N,15.42.

EXAMPLE 3

Cyano bis(2-fluoro-2,2-dinitroethoxy)methane (orbis(2-fluoro-2,2-dinitroethoxy)acetonitrile)

A solution of chloro bis(2-fluoro-2,2-dinitroethoxy)methane (2.45, 6.9mmol) prepared in example 2 and cyanotrimethylsilane (0.77 g, 7.8 mmol)in 15 ml of dichloroethane was refluxed for 40 hours. NMR analysisshowed consumption of the chloroformal and the presence of thecyanoformal together with a small amount of 2-fluoro-2,2-dinitroethylformate. A 2.45 g residue from concentration of the reaction solution ona rotary evaporator was chromatographed on Silica Gel 60 (70-230 mesh,25 g) with a 3:2 solvent mixture of hexanes/dichloromethane to give 1.51g (63%) of bis(2-fluoro-2,2-dinitroethoxy)acetonitrile: mp 41°-2°; IR(film) 2260 (CN, weak) cm⁻¹ ; ¹ H NMR (CDCl₃): δ5.67 (s,l), 4.87 (d, 4,J=16 Hz); mass spectrum (CI, CH₄), m/z (rel intensity): 386 (M+41, 3),375 (M+30, 2), 319 (100 ), 92 (50).

Anal. Calcd for C₆ H₅ F₂ N₅ O₁₀ : C, 20.88; H, 1.46; F, 11.01; N, 20.29.Found: C, 21.05; H, 1.62; F, 10.87; N, 20.38.

To those skilled in the art, many modifications and variations of thepresent invention are possible in light of the above teachings. It istherefore to be understood that the present invention can be practicedotherwise than as specifically described herein and still be within thespirit and scope of the appended claims.

What is claimed as new and desirable to be secured by Letters Patent ofthe United States is:
 1. Bis(2-fluoro-2,2-dinitroethoxy)acetonitrile,N.tbd.C-CH[OCH₂ CF(NO₂)₂ ]₂.
 2. An energetic plasticizer comprising amixture of bis(2-fluoro-2,2-dinitroethyl)formal andbis(2-fluoro-2,2-dinitroethoxy)acetonitrile.
 3. An energetic plasticizeraccording to claim 2 wherein the weight ratio ofbis(2-fluoro-2,2-dinitroethyl)formal tobis(2-fluoro-2,2-dinitroethoxy)acetonitrile is from 1:1 to 4:1.
 4. Anenergetic plasticizer according to claim 3 wherein the weight ratio ofbis(2-fluro-2,2-dinitroethyl)formal tobis(2-fluoro-2,2-dinitroethoxy)acetonitrile is from 3:2 to 4:1.
 5. Anenergetic plasticizer according to claim 4 wherein the weight ratio ofbis(2-fluoro-2,2-dinitroethyl)formal tobis(2-fluoro-2,2-dinitroethoxy)acetonitrile is about 13:7.
 6. A methodof preparing bis(2-fluoro-2,2-dinitroethoxy)acetonitrile comprising thefollowing steps in order:(1) refluxingtris(2-fluoro-2,2-dinitroethoxy)methane with aluminum chloride andacetyl chloride to produce chlorobis(2-fluoro-2,2-dinitroethoxy)methane; (2) reacting one mole ofcyanotrimethylsilane with one mole of chlorobis(2-fluoro-2,2-dinitroethoxy)methane to producebis(2-fluoro-2,2-dinitroethoxy)acetonitrile; and (3) isolating theproduct bis(2-fluoro-2,2-dinitroethoxy)acetonitrile.
 7. The process ofclaim 6 wherein the reaction in step (2) is run under reflux in asolvent selected from the group consisting of dichloromethane,1,1-dichloroethane, 1,2-dichloroethane, 1,1,2-trichloroethane, andmixtures thereof.